1. Field of the Invention
The present invention relates generally to a digital broadcasting, and more particularly to an apparatus for processing program guide data.
2. Description of the Related Art
In a digital broadcast video and audio streams are compressed into digital information to be broadcast, and system information and program information are compressed in accordance with the program and system information protocol (PSIP) standard to be broadcast.
The PSIP is the ATSC standard for terrestrial and cable digital broadcasting, wherein an electrical program guide and system information are defined as one information. That is, the PSIP is defined to provide diverse information on programs by parsing messages encoded by MPEG-2 system (Moving Picture Experts Group; ISO/IEC 13818-1 system) (1977 December., Document A/65).
Specifically, the PSIP includes several tables so that it can transmit/receive audio/video (A/V) data prepared in an AC-3 audio format and in an MPEG-2 video format, respectively, and transmit information on channels of respective broadcasting stations and information on respective programs of the channels.
As described above, the PSIP supports a primary function of providing an A/V service of a desired broadcasting program of a selected channel, and a supplementary function of providing an electronic program guide (EPG) for a broadcasting program, i.e., a broadcasting program guide service. At this time, channel information for channel selection and information such as a packet identifier (PID) for receiving the A/V signal are transmitted through a virtual channel table (VCT), and EPG information of broadcasting programs of respective channels are transmitted through an event information table (EIT), respectively.
The EIT includes information on events of the virtual channel (i.e., such as title, start time, etc.), and one event is a typical television program. The PSIP includes 4 EITs at minimum, and 128 EITs at maximum, and the respective EIT provides event information for a specified period of time.
As described above, the electronic program guide (EPG) for displaying information on a televised program in a digital television (TV) receiver has various presentation types through a table where a plurality of sections are combined for the convenience in interface with a user.
One among the well-known electronic program guide (EPG) types is the Gemster table type.
Also, the digital satellite system (DSS) of DIRECTV, that has the highest market share among the United States satellite broadcasting systems, serves an APG (Advanced Program Guide) that is higher than the existing EPGs in level. Accordingly, the development of a transport demultiplexer (TP) for effectively processing the APG data has been pressed.
Now, the operation of the conventional TP structure for processing the PSI of MPEG, which has the similar structure and contents to the APG, will be explained.
The above-described TP filters the PSI data inputted in the unit of a packet through a PID_filter and a section_filter. At this time, one section_header is mapped to one PID (one PID may be mapped to various section_headers).
The data having passed the filter is stored, being classified according to kinds of section_headers set in a section_filter, and thus buffers are provided as many as the number of the section_headers that can be set.
In this case, the size of the respective buffer should be at least twice the maximum length of the section.
The conventional TP structure as shown in FIG. 1, however, has the following problems.
For convenience' sake, the TP that can set 32 PIDs and 32 section_headers is shown.
First, since it is generally possible to masking the section_filter, only a portion of fields of the section_headers can be actually set. Thus, one set section_header can be combined with several PIDs.
That is, the section matches the PID 0, PID 1, or PID 2, and the filtering may be performed only when the matched PID matches the header 0 of the section_filter.
However, according to the structure of the conventional data processing apparatus, since only one PID matches one section_header, the section_header 0 having the same PID_filter matches the PID 0, PID 1, and PID 2 of the PID-filter one by one, and thus three section_headers should be set in total. This results in that only 29 headers among 32 headers remain to be set.
As described above, according to the conventional TP, since the section_header matches only one PID even if the TP has a memory that enables 32 headers to be set, this causes 32 memories not to be used in full if the header value is set twice or more. However, since various kinds of objects are inputted to the APG, the kinds of frame_headers to be set become great, and thus it is difficult that the frame filter performs its own function well.
Second, since the number of buffers for storing the PSI data should be always equal to that of headers of the section_filter, the size of the buffer becomes massive.
In this case, the size of the buffer becomes 32× (i.e., the size determined by the user: the minimum size whereby the buffer becomes not in full), and this causes a stumbling block in reducing the size of hardware.
As a result, the conventional program guide data processing apparatus has the following disadvantages.
First, since one section_header matches only one PID, the memory for setting the headers cannot be used in full.
Second, since the number of buffers for storing the PSI data is always equal to the number of headers of the section_filter, the total size of the buffer becomes massive, and it is difficult to reduce the size of hardware.